In a matter of days, President Donald Trump will roll out major components of his emerging Iran policy. He’s expected to announce that he will decertify the Joint Comprehensive Plan of Action (JCPOA), or the nuclear deal with Iran, passing the buck to Congress on whether or not to re-impose sanctions on the country. So far, the administration has begrudgingly certified Iranian compliance with the deal twice.

Just two weeks later on October 30, Trump will also reportedly designate Iran’s Islamic Revolutionary Guards Corps (IRGC) as a terrorist organization. He’ll do this despite the fact that the Guards are indirectly helping him accomplish another of his key objectives: defeating the Islamic State (ISIS). Indeed, the Guards have been a major force in the fight against the group in Iraq, and will remain a critical player there after ISIS. They are also a critical force in Afghanistan, another key theater for America.

But Trump’s designation, which could lead to the imposition of sanctions on the organization, is likely to significantly undermine Washington’s ability to coordinate or even deescalate with Tehran in places where they have both deployed forces. (And since the IRGC is already subject to U.S. sanctions, the impact will be more political than economic.) The Guards’ commander, Major General Mohammad Ali Jafari, already pledged to reciprocate by designating the U.S. military as a terrorist organization on par with ISIS. He’s also warned that his country would choose to settle regional issues not at the negotiating table but by other means. The Guards also flexed their muscles in the Persian Gulf, where their Navy conducted drills using over 100 rocket-launching speedboats, mining vessels, and missile launchers.

Since the IRGC’s formal establishment following the 1979 Islamic Revolution, it has sparked controversy both at home and abroad. In the United States, it has become synonymous with the regime’s most nefarious activities, including the development of ballistic-missile capabilities in defiance of the international community, and support of terrorist groups like Hezbollah. American policymakers have proposed a range of actions to curtail the IRGC, including political pressure, sanctions, military action, and, now, potentially pulling out of the JCPOA. But in the past, none of those plans have managed to slow the IRGC. They’ve often been counterproductive, expanding the Guards’ influence and scope and depth of their activities.

Rather than undermining the nuclear deal, the Trump administration could, in fact, seize the opportunity it presents for Tehran to continue re-calibrating. In the process, it’ll prove that full recovery will never take hold as long as the Guards are in charge.

For nearly four decades, the Guards’ influence has seeped into the most vital areas of Iranian life. Their hold on Iran’s armed forces and security apparatus increased their political leverage, allowing them to gain control of key sectors of the economy. But the IRGC’s most critical strengths lie in its resilience and ability to turn national misfortune and calamity into opportunities to consolidate its power.

The history of the IRGC’s growth from a revolutionary militia into an integral part of Iran provides key insights into its strengths and weaknesses, which the United States can leverage to check the organization. The Guards were created bottom-up to combat and, ultimately, topple the Shah, Iran’s pro-Western monarch whose family ruled the country for decades. Following the fall of the Shah, the Islamic Republic formally established the IRGC to balance against the traditional military, which the revolutionaries saw as loyal to the monarch and the people, not the nascent regime of Supreme Leader Ayatollah Ruhollah Khomeini.

During the Iran-Iraq War, an eight-year conflict initiated by Saddam Hussein that cost hundreds of thousands of lives and billions of dollars in damage to Iran, the Guards grew into an important part of the military. In the eyes of the world, they became known as a band of irrational ideologues, whose mystical, suicidal tendencies compelled them to drive their child soldiers onto the enemy’s minefields. But the Guards also revealed their pragmatic side, motivated by the goal of ensuring the regime’s survival and security. By the end of the war, the IRGC had started or resumed many of Iran’s key military initiatives—programs to build nuclear weapons and other weapons of mass destruction, and others to build missiles and drones—turning it into the driving force of the country’s military-industrial complex. Today, this IRGC-led enterprise produces most of Iran’s indigenous military equipment and weapons.

After the war, the Guards placed themselves at the forefront of state efforts to rebuild. Reconstruction afforded them the opportunity to enter key sectors of the Iranian economy, in particular infrastructure and energy. And the imposition of international nuclear-related sanctions starting in the mid-2000s led to the IRGC tightening its grip over the country’s economic engine.

By the time the Obama administration had galvanized the international community to impose the sanctions that ultimately led to the nuclear talks in 2012, the IRGC’s control of a number of key sectors, from infrastructure, to energy, to import-export, to telecommunications, was indisputable. The IRGC left no opportunity unexploited, setting up or expropriating hundreds of companies both inside and outside Iran and negotiating contracts with the government and other entities. The sanctions only strengthened the IRGC’s grip, allowing it to step in to the vacuum left by international investors and businesses. Over time, it gained control over illicit and black-market financing networks and sidelined the private sector. Today, the IRGC is worth and holds billions of dollars in contracts, although the exact numbers and actual reach of the Guards is disputed. This, in turn, bought them more political capital and influence.

As a result, neither the war nor the subsequent sanctions and political isolation weakened the Guards—they did just the opposite. The war, combined with the efforts to isolate Iran, turned the IRGC into the powerhouse it is today. This is precisely what American lawmakers and policymakers fail to understand about the IRGC.

The rise of ISIS in Iraq and Syria as well as that of its offshoot in Afghanistan, complicates matters. Indeed, the Guards have grown even more powerful thanks to the fight against ISIS. Iran has managed to successfully deter and prevent ISIS attacks against its territory—with the exception of the June 2017 twin attacks in Tehran—and to stay afloat in a region forever descending into deeper chaos. And the IRGC, as the face of Iran’s efforts against ISIS, has risen in popularity at home, even among those who don’t support the regime or its meddling abroad. This makes it far more difficult for America and its allies to effectively isolate and delegitimize the Guards.

Indeed, conservative U.S. foreign policy circles often mistake calls for a different approach to Iran—one not based on isolation and sanctions, but on a combination of methods, chiefly engagement—as calls for letting the Islamic Republic off the hook. And they call for foregoing viable channels of communication to focus, instead, on ramping up pressure on the regime. But noting that the business-as-usual approach toward Tehran hasn’t worked doesn’t mean that the Guards should be left unchecked. Likewise: Pointing out that applying more pressure, in perpetuity—as American hardliners advocate—is not a sustainable and effective policy outcome, but rather just a tactic that’s often failed, doesn’t mean anyone’s given up.

To be sure, many of the IRGC’s activities in Iran and its neighborhood are a source of concern for the United States and its allies. But there’s no quick fix to the issue. Instead, Washington should seek a more long-term approach that relies on the international community to preserve and build on the nuclear deal, showing the regime that there are alternatives.

By building on the nuclear deal, as the European Union has done since it was reached in July 2015, the international community can undermine Iran’s hardliners who see self-reliance as the only way forward and the IRGC as central to the pursuit of self-sufficiency. Preserving the JCPOA can also help empower the moderates, who, backed by the Iranian public, wish for more international integration, including economic interdependence and political engagement. Key decision-makers in Iran understand that none of this will materialize without deep-reaching reform. In fact, the moderate President Hassan Rouhani has made curbing the IRGC’s reach a top priority. To do so, he named a traditional military commander, not a Guard, to lead the Ministry of Defense—a first in over two decades. Likewise, he has sought to cut funding for the IRGC and has tried to rein in its sprawling business and financial networks.

But de-coupling the Iranian state from the IRGC won’t happen overnight. So long as the Islamic Republic is in power, it is futile to try to eradicate the Guards from Iran’s security landscape. Instead, the United States would be better served by undermining it to the extent it can. By imploding the JCPOA, the United States will play into the hands of the IRGC—the very actor it’s trying to contain.

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Ariane M. Tabatabai is an associate political scientist at the RAND Corporation.